Visualizations to help simplify complicated app logic

Hi all – new here and haven't found an answer yet. Does anyone use any graphics to keep track of the logic / architecture in complex apps? My app is quite large, with multiple docker containers and microservices and I'm curious what tools people use to visualize or simplify the code logic.

I have a lot of technical debt in my current project and just want to outline everything and start reducing code.

Thanks!